The transport of solid material through a closed conduit or pipe has long been known in the art of material handling. Some of the materials transported are of an abrasive nature and the occurrence of erosion of the pipe or conduit sidewalls is well known. This undesirable erosion is commonly experienced throughout the material transport system but is most acute in the nonlinear or angular pipe segments wherein the direction of flow of the abrasive material is altered.
In an attempt to reduce or eliminate the erosion of nonlinear pipe segments or elbows, a wide variety of shaping, diverting and strengthening strategies have been developed over the years. In general, the problem of erosion has been attacked through the use of a pipe comprising an inner liner, circular in cross-section, fabricated of an abrasion resistant material and an outer supporting shell.
U.S. Pat. No. 4,554,721 discloses a wear resistant pipe segment which has an inner, one piece wear resistant liner composed of a ceramic material and an outer supporting shell. The outer shell is longitudinally split to allow removal and replacement of the ceramic inner liner. A bed of refractory or other cushioning material between the liner and the shell cushions the interface and fills any gaps which may be present. The outer shell is fabricated as any standard segment of pipe even including the welding of flanges onto the metallic shell. The shell may then be split to allow insertion of bedding material and the inner liner. The two halves of the outer shell are then clamped together and secured to form the finished pipe segment. This patent does not suggest or disclose a flat impingement surface that is sloped at specific angles relative to the direction of the incoming flow.
U.S. Pat. No. 4,199,010 discloses wear resistant pipe bends comprising a monolithic liner of nitride-bonded silicon carbide attached to the inside wall of a curved pipe segment. The '010 patent discloses a monolithic ceramic liner of abrasion resistant material disposed within an outer metal shell having a bed of refractory material in the annular space there between. This patent further discloses an outer shell of curved pipe formed from a plurality of smaller straight pipe sections which are mitered angularly and assembled into a nonlinear shell around the monolithic inner liner.
U.S. Pat. No. 3,920,191 discloses a liner for ball mills, pebble mills, vibration mills and the like which consists of hollow, inflatable resilient bodies made of a suitable elastomer, such as rubber. The elastomeric body is inflated hydraulically or pneumatically. In a typical case the mill is lined with a hollow tube formed into a helix.
U.S. Pat. No. 3,559,694 discloses a removable insulation unit for surrounding pipe joints, particularly at fittings such as elbows, tees and the like which comprises a pair of relatively thin outer shells which are connectable by fastening means to form a cylinder cover. An insulation liner surrounded by a perforated member is secured within each shell member by hook members that extend inwardly from its inner wall.
U.S. Pat. No. 3,350,832 discloses a lining for a wall exposed to wear which comprises inner spaced panels and strips of elastomeric wear resistant material. Metal abutments are anchored on the strips and overlie metal flanges, anchored to and protruding from the panels along the walls. Clamping means engage the wall and the abutment for clamping the metal flanges between the wall and the abutments.
U.S. Pat. No. 1,518,705 discloses a pipe having a plurality of corrugations cast integral with the interior walls of said pipe. The corrugations are positioned with an angle less than 180.degree. in the upper and lower portions of said pipe.
U.S. Pat. No. 1,246,189 discloses an elbow having a branch opening and an aperture in the elbow bend, wherein a wear liner is removably arranged within the elbow.
The use of an inner liner of abrasion resistant material, while significantly slowing the erosion of the nonlinear pipe segment, does not stop the occurrence of significant wear over an extended period of time. In each of the prior art designs, the removal and subsequent replacement of the inner erosion resistant liner proves to be difficult and costly.
Materials used for wear protection have been rubber, metal alloys, ceramics and plastics. The elastic materials used for wear protection are in contrast to other wear materials, soft and elastic, and frequently display greater resistance to abrasion than the hardest of the steel materials. Instead of using a high degree of hardness to consume kinetic energy by deforming and chipping the wear surface, rubber swallows the load by deflecting and returning to its original shape. Of major importance to the wear process is the angle of impact of the solid particles or impingement angle. The literature has disclosed that less wear is obtained with rubber as compared to any other wear material when the angle of impact is less than 5.degree. or greater than 50.degree.. Wear may be defined as the undesirable removal of material in the form of fine particles from the surface of a body by mechanical means.
The prior art pipe segments, while effectively reducing interior wear through the use of a wear resistant lining material have not eliminated it completely and replacement is sometimes a difficult and costly endeavor. The prior art has failed to appreciate that an elastomeric elbow with a flat impingement surface must have all angles of incidence of at least 35.degree., but not more than 65.degree. and which has a cross-sectional area through the impingement surface of at least 1.25 times greater than the cross-sectional area of the inlet would provide superior performance in the conveyance of abrasive material.
The invention, its advantages and its features will be apparent to those skilled in the art from a consideration of this specification including the attached drawings and appended claims.